If the Motronic system provides full spark advance when using 91 octane, which it does, higher octane gasoline gives no benefit. Higher octane fuel is less susceptible to preignition and detonation and that is really its only benefit. Unless your car is modified with higher compression pistons or the Motronic ECU has had its advance curve modified, the 100 octane fuel is just wasting money.

I don't know why people think you need more octane if the factory ignition ECU map is set for 91-93 pump gas? From my racing experience with GM LS7 engines, higher octane fuel will slow ignition burn rate and result in less peak hp on a dyno if it does not detonate on 93 octane. 100 octane and above is only needed for higher cylinder pressures like for supercharging or turbocharging. An old racers trick is to buy Toluene at Ace or Home Depo for about $20 gallon and add 1 gal toluene to 5 gallons of 91 octane to produce ((1*114 + 5*91))/(1+5) = 94.8 octane which is more than enough octane for a factory ECU. Save some money and make your own. $230 for a tank of 100 unleaded is crazy!

I don't know why people think you need more octane if the factory ignition ECU map is set for 91-93 pump gas? From my racing experience with GM LS7 engines, higher octane fuel will slow ignition burn rate and result in less peak hp on a dyno if it does not detonate on 93 octane. 100 octane and above is only needed for higher cylinder pressures like for supercharging or turbocharging. An old racers trick is to buy Toluene at Ace or Home Depo for about $20 gallon and add 1 gal toluene to 5 gallons of 91 octane to produce ((1*114 + 5*91))/(1+5) = 94.8 octane which is more than enough octane for a factory ECU. Save some money and make your own. $230 for a tank of 100 unleaded is crazy!

87 Octane is actually a more powerful and efficient burning gas, unfortunately that also means it detonates as soon as you start making some decent power! Be careful running anything over 93 for extended periods as it heats the catalytic convertor above its normal operating temp and could cause a cat failure.

I don't know why people think you need more octane if the factory ignition ECU map is set for 91-93 pump gas? From my racing experience with GM LS7 engines, higher octane fuel will slow ignition burn rate and result in less peak hp on a dyno if it does not detonate on 93 octane. 100 octane and above is only needed for higher cylinder pressures like for supercharging or turbocharging. An old racers trick is to buy Toluene at Ace or Home Depo for about $20 gallon and add 1 gal toluene to 5 gallons of 91 octane to produce ((1*114 + 5*91))/(1+5) = 94.8 octane which is more than enough octane for a factory ECU. Save some money and make your own. $230 for a tank of 100 unleaded is crazy!

My car runs with a dyno custum EUC tune.
I increase my heads flow by 11% intake and exhaust with a better intake system and free flow exhaust. It limits up to 9.2k rpm.
I think you need a good race gas to get the best of all the upgrades, don't you?

+1... Higher than 93 octane is not helping you and could reduce maximum HP.

Quote:

Originally Posted by tazandjan

If the Motronic system provides full spark advance when using 91 octane, which it does, higher octane gasoline gives no benefit. Higher octane fuel is less susceptible to preignition and detonation and that is really its only benefit. Unless your car is modified with higher compression pistons or the Motronic ECU has had its advance curve modified, the 100 octane fuel is just wasting money.

+1; just wasting $

Quote:

Originally Posted by Evan@Fabspeed

87 Octane is actually a more powerful and efficient burning gas, unfortunately that also means it detonates as soon as you start making some decent power! Be careful running anything over 93 for extended periods as it heats the catalytic convertor above its normal operating temp and could cause a cat failure.

+1; Higher octane gas is less energy dense.

Quote:

Originally Posted by Ingpr

My car runs with a dyno custum EUC tune.
I increase my heads flow by 11% intake and exhaust with a better intake system and free flow exhaust. It limits up to 9.2k rpm.
I think you need a good race gas to get the best of all the upgrades, don't you?

Only if your ECU tune sets your timing advance to take advantage of higher octane fuel, and then the gain is minimal from the fuel itself. This is assuming we are not talking about a top fuel dragster, or forced induction in general. In forced induction the general goal is higher boost, and the limitation "wall" is detonation. Thus higher octane reduces the chance of detonation and thus allows more boost, making more HP/TQ.

+1... Higher than 93 octane is not helping you and could reduce maximum HP.

+1; just wasting $

+1; Higher octane gas is less energy dense.

Only if your ECU tune sets your timing advance to take advantage of higher octane fuel, and then the gain is minimal from the fuel itself. This is assuming we are not talking about a top fuel dragster, or forced induction in general. In forced induction the general goal is higher boost, and the limitation "wall" is detonation. Thus higher octane reduces the chance of detonation and thus allows more boost, making more HP/TQ.

True, but these car you mention don't rev that high. You don't want your Ferrari engine detonate at 9k. Right?

True, but these car you mention don't rev that high. You don't want your Ferrari engine detonate at 9k. Right?

The high RPMs do not really change the octane requirements. High RPMs require many other modifications namely:
1. Springs that can get the valves closed fast enough as to not float. F1 RPMs require a gas to close them!
2. Stroke is usually reduced to lower inertial loads on the piston and rods.
3. Valves are titanium or filled with a light material, sometimes sodium.
4. Lightning of rotational parts; Pistons, Rods, Crank
5. Reducing parasitic losses from high RPMs like pulling a partial vacuum on the crank case, lighter oil, electric accessories (AC, Oil Pump, Water Pump).

Then once you get those stratospheric RPMs like in F1 or Superbikes then you end up with a "tuned" RPM range, where at lower RPMs the motor is in a non linear power delivery range. Thus while driving it the RPMs must be kept above a minimum to keep the engine in its tuned range. Look at the HP / TQ curves for a F1 car or a super bike, or other vehicle with >10k limit. At lower RPMs you are making much less power / rpm than at high rpm.

*my S1000RR revs to 14K RPM and its one liter 4 cyl and runs fine on 91 octane. Here is a video of a 14k redline on my superbike with overhead cams. Its INSANE!

I have a tune in my CS for 93 octane fuel (and no cats) but the best "normal" out here in Vegas is 91. There are a few gas stations that sell 100 so I mix 9 gallons of 100 with 13 gallons of 91 to make 94 to keep it above the 93 it's tuned for. I've taken the car to 8500 rpms many times with no issues and have received lots of advice that my mixture is safe for the motor as long as I keep it above 93.

Back in the early 2000's many Sunoco stations in CT used to sell 94 octane for about 5 cents more than 93. The 91 was like 5 cents lower than 93. I used to use the 94 all the time in my 2001 BMW 330xi and never had any issues with it. I cannot seem to find the 94 octane stuff anymore. I wonder why?

What most people don't understand is that "race" gas is not the same as regular gas.

"100 octane" is simply a "knock" rating. Too many assume that gas quality is the same between 100 octane vs 91 octane. It's not.

There are different types of 100 octane gasoline. Some get the knock rating that high simply by adding Tetraethyl Lead. This is the case with some aviation fuel.

100 octane unleaded race gas is not the same. It has better burn capabilities.

A typical 92 or 93 octane pump gas contains hydrocarbons that evaporate in a range from about 80 degrees F to over 400 degrees F. Good 100 Octane unleaded race gas contains hydrocarbons that evaporate from about 100 degrees F to 270 degrees F.

The higher evaporation temperature means that it takes longer for vaporization to take place as well needing a higher temperature to do so. At wide open throttle, and as RPM increases, there is increasingly little time for evaporation to take place. The 100 octane race gas will vaporize more readily, and convert more chemical energy to mechanical energy than the 92/93 octane fuel, and therefore the 100 octane will make more power.

Feel free to research.

Now..how much more power is debatable.

I look at it this way. Here in California, we only have 91 octane. Mixing it with 100 octane unleaded race gas should produce some additional power. Is it worth the extra money? Probably not.

One other thing to note. When I first got my E46 M3 back in 2001, the octane rating for premium was actually 92 not 91. So Ferrari 360 engines were probably built with 92 octane minimum ratings in mind also...at least the earlier builds. I recall this octane rating changing some time in late 2001 or early 2002 here in California. I can't recall specifically.

I'm not sure what the standards in europe are. I know the octane ratings are slightly different. I do get the impression the Ferraris were/are tuned from the factory with a higher octane rating than what we have here in California.

Rod- Do some research. European octane is calculated using a completely different system than US octane rating, which is an average of two measures of octane. 100 octane unleaded, racing fuel or not, is a waste of money in a stock Ferrari and will not get you any additional hp.